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Chapter 12
Work and Machines
| Term | Definition |
|---|---|
| work | force exerted on an object that causes it to move |
| joule | unit of work equal to one newton-meter |
| power | the rate at which one form of energy is transferred into another object |
| machine | a device that changes the amount of force exerted, the distance over which a force is exerted, or the direction in which the force is exerted |
| input force | the force exerted on a machine |
| output force | the force exerted on an object by a machine |
| input work | the work done on a machine as the input force acts through the input distance |
| output work | the work done by a machine as the output force acts through the output distance |
| mechanical advantage | the number of times a machine increases a force exerted on it |
| efficiency | the percentage of the input work that is converted to output work |
| inclined plane | a simple machine that is a flat, sloped surface |
| wedge | a simple machine that is an inclined plane that moves |
| screw | a simple machine that is an inclined plane wrapped around a central cylinder to form a spiral |
| lever | a simple machine that consists of a rigid bar that pivots about a fixed point |
| fulcrum | the fixed point around which a lever pivots |
| wheel and axle | a simple machine that consists of two attached circular or cylindrical objects that rotate about a common axis, each one with a different radius |
| pulley | a simple machine that consists of a grooved wheel with a rope or cable wrapped around it |
| compound machine | a device that combines two or more simple machines |